Lord Falconer's constitutional reforms were in disarray last night after an alliance of former law lords, cross benchers and Conservatives vowed to block government plans for a supreme court next week by referring the issue to a special select committee.

The leader of the Commons, Peter Hain, described the manoeuvre, which would make it highly unlikely for the bill to be passed in this session, as unprecedented. He said the lords had no right to block the government's programme, especially a flagship bill.

In a separate set-back Lord Falconer has also been forced to defer a bill abolishing the hereditary peerage after a series of drafting errors.

He is also struggling to find any political support in the Lords for separate plans to oust the judiciary from immigration appeals cases.

The crisis for Lord Falconer came to a head when the lord chief justice, Lord Woolf, on Wednesday launched a scathing attack on the panapoly of the government's judicial reforms, warning a supreme court could create new tensions between the judiciary and parliament.

Lord Woolf backed deferral of the supreme court bill, due for its second reading in the Lords on Monday, if no suitable new building for the new supreme court has been identified. The government wants to take the 12 law lords out of the Lords in a bid to separate judiciary from the executive.

In a move denounced by Mr Hain as wrong, the former law lord Lord Lloyd of Berwick has tabled a motion, with Conservative support, calling for the bill to be referred to a select committee for further scrutiny. Mr Hain conceded that if Lord Lloyd's motion is supported: "It will be impossible to get this bill through parliament in this session."

Lord Lloyd, a law lord between 1993 and 1998, has the open support of at least five serving law lords, many of whom do not want to be ejected from the Lords.

Lord Strathclyde, the Conservative leader in the Lords warned: "There's an old rule in politics. When you are in a hole stop digging.

"Tony Blair would make a big mistake if he tried to tough these things out. He must listen to real and growing fears that his plans threaten judicial independence.

"If they do foolishly try to press on with this discredited bill it must be subject to pre-legislative scrutiny as both Commons and Lords have asked and Lord Lloyd now proposes."

The Conservatives claim the bill should be put into committee for scrutiny since it had not been in the Labour election manifesto and not been the subject of a consultative white paper.

The proposal was announced last June in the botched Cabinet reshuffle that saw the sacking of Lord Irvine, the former lord chancellor and old friend of Mr Blair.

Opponents of the government's constitutional modernisation claim Lord Falconer is not standing up to the authoritarian power grab of the home secretary, David Blunkett.

Ministers plan to mount a major campaign to reassure Labour backbench MPs over their friendless asylum reform plans after the swingeing attack from Lord Woolf that they "fundamentally conflict with the rule of law".

Both Mr Blunkett and Lord Falconer kept their heads down yesterday to avoid fuelling the renewed clash with the judiciary, but Lord Woolf will have widespread backing from peers across all parties when the controversial asylum legislation reaches the Lords on Monday week.

Downing Street said ministers would listen to Lord Woolf's criticisms of the proposal to remove the right for asylum seekers to take their case to the high court, but insisted the current two-tier appeal system was too complex and meant cases could be drawn out for a year or longer.